1. Field of the Invention
The present invention relates generally to correction of spinal deformities and, more particularly, to an apparatus and a method for applying sustained tension on a tether used in a treatment site.
2. Description of the Related Art
Tools and methods have been developed for tensioning flexible elongate media (hereinafter generically referred to as a tether) used in various surgical applications. One such surgical application is correction of pediatric deformities. During such surgical procedure, it is required that the tether has a predetermined tension before fixing it in place. Tensioning tools, in particular, need to provide a way to impart some predetermined measurable tension on the tether and maintain this tension before the tether is fixed or constrained in some manner to a target, such as bone or an implanted anchor device, during a medical procedure in a treatment site.
However, at various times after the desired predetermined tension has been applied on the tether, the tether will elongate under the load, changing form or location, bones or implant move relatively each other and, as a result, the tension in the tether changes. The fact that this undesirable event may occur from time to time demonstrates the need for a technique and means to carry out permanent tension measurement and adjustment before and during the time when the tether is fixed or constrained.
Thus, there is still a need for an innovation that will overcome the above-described problem.